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BUG: KASAN: use-after-free in l2cap_chan_close+0x564/0xb10 net/bluetooth/l2cap_core.c:794
Read of size 1 at addr ffff888040441020 by task kworker/0:7/3844

CPU: 0 PID: 3844 Comm: kworker/0:7 Not tainted 5.8.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
Workqueue: events do_enable_set
Call Trace:
 __dump_stack lib/dump_stack.c:77 [inline]
 dump_stack+0x18f/0x20d lib/dump_stack.c:118
 print_address_description.constprop.0.cold+0xae/0x436 mm/kasan/report.c:383
 __kasan_report mm/kasan/report.c:513 [inline]
 kasan_report.cold+0x1f/0x37 mm/kasan/report.c:530
 l2cap_chan_close+0x564/0xb10 net/bluetooth/l2cap_core.c:794
 do_enable_set+0x4ed/0x980 net/bluetooth/6lowpan.c:1082
 process_one_work+0x94c/0x1670 kernel/workqueue.c:2269
 worker_thread+0x64c/0x1120 kernel/workqueue.c:2415
 kthread+0x3b5/0x4a0 kernel/kthread.c:291
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:293

Allocated by task 17:
 save_stack+0x1b/0x40 mm/kasan/common.c:48
 set_track mm/kasan/common.c:56 [inline]
 __kasan_kmalloc.constprop.0+0xc2/0xd0 mm/kasan/common.c:494
 kmem_cache_alloc_trace+0x14f/0x2d0 mm/slab.c:3551
 kmalloc include/linux/slab.h:555 [inline]
 kzalloc include/linux/slab.h:669 [inline]
 l2cap_chan_create+0x40/0x3a0 net/bluetooth/l2cap_core.c:450
 chan_create net/bluetooth/6lowpan.c:648 [inline]
 bt_6lowpan_listen net/bluetooth/6lowpan.c:967 [inline]
 do_enable_set+0x52f/0x980 net/bluetooth/6lowpan.c:1086
 process_one_work+0x94c/0x1670 kernel/workqueue.c:2269
 worker_thread+0x64c/0x1120 kernel/workqueue.c:2415
 kthread+0x3b5/0x4a0 kernel/kthread.c:291
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:293

Freed by task 17:
 save_stack+0x1b/0x40 mm/kasan/common.c:48
 set_track mm/kasan/common.c:56 [inline]
 kasan_set_free_info mm/kasan/common.c:316 [inline]
 __kasan_slab_free+0xf5/0x140 mm/kasan/common.c:455
 __cache_free mm/slab.c:3426 [inline]
 kfree+0x103/0x2c0 mm/slab.c:3757
 l2cap_chan_destroy net/bluetooth/l2cap_core.c:488 [inline]
 kref_put include/linux/kref.h:65 [inline]
 l2cap_chan_put+0x1b2/0x230 net/bluetooth/l2cap_core.c:502
 do_enable_set+0x4f9/0x980 net/bluetooth/6lowpan.c:1083
 process_one_work+0x94c/0x1670 kernel/workqueue.c:2269
 worker_thread+0x64c/0x1120 kernel/workqueue.c:2415
 kthread+0x3b5/0x4a0 kernel/kthread.c:291
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:293

The buggy address belongs to the object at ffff888040441000
 which belongs to the cache kmalloc-2k of size 2048
The buggy address is located 32 bytes inside of
 2048-byte region [ffff888040441000, ffff888040441800)
The buggy address belongs to the page:
page:ffffea0001011040 refcount:1 mapcount:0 mapping:0000000000000000 index:0x0
flags: 0xfffe0000000200(slab)
raw: 00fffe0000000200 ffffea0002576d48 ffffea0001bec348 ffff8880aa000e00
raw: 0000000000000000 ffff888040441000 0000000100000001 0000000000000000
page dumped because: kasan: bad access detected

Memory state around the buggy address:
 ffff888040440f00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
 ffff888040440f80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
>ffff888040441000: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
                               ^
 ffff888040441080: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
 ffff888040441100: fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb fb
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